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Chlorophyll molecules can be found in ancient sediments and can be used to help reconstruct past environments. 

The structure of these biomarkers of past photosynthesis includes information on past growth conditions.

Hydrogen is incorporated into the molecule during biosynthesis and the isotopic composition of the water within the cell at that time is reflected in the hydrogen isotopic composition of the final molecule.

The ratio of deuterium to hydrogen of individual compounds can be determined by gas chromotography-isotope mass spectrometry.